RANK Ligand Blockade with Denosumab in Combination with Sorafenib in Chemorefractory Osteosarcoma: A Possible Step Forward?

Abstract

Background: There is no established systemic treatment option for unresectable osteosarcoma progressing after standard chemotherapy. A recently published clinical trial has demonstrated some activity of sorafenib in this situation. Preclinical research suggests a role for the inhibition of the receptor activator of nuclear factor-ĸB ligand (RANKL), but no clinical data have been reported so far. Case Report: A 37-year-old man was diagnosed with unresectable osteoblastic, osteoblastoma-like osteosarcoma in the C7/Th1 vertebra. The tumour progressed locally despite two lines of chemotherapy and stereotactic radiotherapy. On treatment with sorafenib and denosumab, a complete metabolic remission was achieved and is ongoing for over 18 months. Immunohistochemistry revealed an overexpression of RANK and RANKL in the patient's primary tumour. Discussion: This is the first report of activity achieved by the combination of the tyrosine kinase inhibitor sorafenib and the RANKL inhibitor denosumab in a patient with osteosarcoma. It confirms preclinical data on RANK/RANKL inhibition in osteosarcoma and could serve as a hypothesis-generating approach for clinical trials in this patient population.